There is always a risk of leakage in systems for production and distribution of liquid and gaseous fluids. A major problem here is corrosion and anodic or cathodic protection is used as corrosion protection on oil and gas pipes, onshore or offshore and also on stressed steel structures, offshore. Either this corrosion protection is produced by an electric current or by sacrificial anodes, it is vital that the protection does not degenerate as time pass. Causes for degeneration may be damages to the mechanically applied surface protection, faults in sacrificial anode systems etc.
Therefore the electrochemical protection of steel structures and pipes must be checked closely and several methods have been developed for this surveillance. Visual inspection by divers or by remotely operated vehicle and TV-camera is often used. Also detection of the electrode potential of the steel or the electric density in the ambient water. Both said methods normally require the use of supply ships, divers or robots. The necessity of making this inspection over long distances at submerged oil or gas pipes, makes each inspection very expensive since it involves large efforts in manpower and technical means at considerable risk. In case of a buried pipe, it is often not available for outer inspection.
In view of the above, a permanently installed electronic monitoring system would render several advantages in comparance with the present systems. Thus the total expenses for inspection would be considerably reduced during the lifetime of the installation; the risk for human and equipment damages would be avoided; continuous inspection is possible, and buried pipes could also be inspected. The problem so far has been to make a simple and endurable monitoring system for this environment.